Thermally broken truss

ABSTRACT

A thermally broken truss ( 10 ) for a cage of a structural building panel, comprising: first and second elongate outer support members ( 12, 14 ); first and second elongate intermediate support members ( 16, 18 ) interposed between the first and second outer support members ( 12, 14 ); at least one first connecting member ( 20 ) interconnecting the first outer support member ( 12 ) and the first intermediate support member ( 16 ); at least one second connecting member ( 22 ) interconnecting the second outer support member ( 14 ) and the second intermediate support member ( 18 ); and a thermally insulative fastener ( 24 ) which fastens the first and second intermediate support members ( 16, 18 ) together in spaced apart relationship, thereby providing a thermal break between the first and second outer support members ( 12, 4 ). A thermally broken structural building panel ( 40 ) is also provided.

The present invention relates to a thermally broken truss, and more particularly but not necessarily exclusively to a thermally broken truss for a cage of a thermally broken structural building panel. The invention also relates to the thermally broken structural building panels themselves, using such a thermally broken truss.

It is known to construct buildings, such as houses and commercial and industrial buildings and structures, using prefabricated building panels. Such panels are formed off-site, ready for use as and when required. Typically, the panels are used in the floors, in the building walls, in the foundations and in the roof. A key reason why prefabricated building panels are widely used is that they help to reduce the time required on site for building construction.

The known prefabricated panel is limited in terms of its insulation properties.

At present, increasing the energy efficiency of buildings has become one of the most widespread goals in the construction industry. However, efforts to reduce building energy use are typically focused on the mechanical, electrical and glazing systems and not the structural system.

Typical methods of construction for buildings, such as residential houses and commercial and industrial buildings, using prefabricated building panels are either not sufficiently energy efficient or too costly for an average buyer once the cost of the necessary components to make them energy efficient is accounted for.

A thermal break or thermal barrier is an element of low thermal conductivity placed in an assembly to reduce or prevent the flow of energy between conductive materials. Thermal breaks made of polyamide or polyurethane are known to be in the order of a thousand times less conductive than aluminum and a hundred times less than steel. Providing a thermal break in a truss for a cage of a structural building panel will lead to improved efficiency, performance and costs savings.

It is an object of the present invention to provide a thermally broken truss and/or a structural building panel which reduces or substantially obviates the above mentioned problems. In brief, it is the object of the invention to provide a structural building panel which meets the industry demands for improved heat insulation properties, and which also has a low manufacturing cost and a low weight.

According to a first aspect of the invention, there is provided a thermally broken truss for a cage of a structural building panel, comprising: first and second elongate outer support members; first and second elongate intermediate support members interposed between the first and second outer support members; at least one first connecting member interconnecting the first outer support member and the first intermediate support member; at least one second connecting member interconnecting the second outer support member and the second intermediate support member; and a thermally insulative fastener which fastens the first and second intermediate support members together in spaced apart relationship, thereby providing a thermal break between the first and second elongate outer support members.

The thermally broken truss is advantageous as providing a thermal break in a truss for a cage of a structural building panel will reduce or prevent the flow of unwanted energy. If the thermally broken truss is used in a structural building panel, a break in the thermal path will prevent or reduce heat energy from transferring between the interior and the exterior of the building. Whilst, thermal breaks are traditionally used in colder climates, they are equally important in warm environments to reduce heat transfer in air conditioned buildings and can lead to improved energy efficiency, performance and costs savings.

Preferably, the thermally insulative fastener may be a sheath in which the first and second intermediate support members are received.

Beneficially, this provides that both the first and second intermediate support members are housed in an insulative material, greatly reducing the flow of energy between the first and second intermediate barriers and providing a thermal barrier therebetween.

The thermally broken truss may further comprise at least one reinforcement element which buttresses the thermally insulative fastener and is held in a spaced relationship from the first and second intermediate support members by the thermally insulative fastener. Preferably, the reinforcement element may be a strap or a collar and may be composed of, or include, metal. Further, the reinforcement element may encircle at least part of the first and second intermediate support members.

Advantageously, this reinforcement element may provide support to the thermally broken truss and protect the integrity of the thermally insulative fastener, and may help prevent tensile stress from disrupting the structure of the thermally broken truss.

Most preferably, the reinforcement element may be spaced apart from the first and second connecting members. This is beneficial, in reducing energy flow from the first and second intermediate members to the first and second outer support members via the first and second connecting members.

In one embodiment, the thermally insulative fastener may be provided in a gap between the first and second intermediate support members. In addition, the thermally insulative fastener may be composed of or include polystyrene, polyurethane foam, or polyamide. Further the thermally insulative fastener may be composed of or include adhesive. Advantageously, these materials are far less conductive than metal and, as above, provide a thermal break between the first and second intermediate support members, thereby preventing or reducing the flow of thermal energy from the first intermediate support member to the second intermediate support member, or vice versa.

The thermally insulative fastener may be connected to at least one of the first or second intermediate support members using a connective means. Preferably, the connective means may include adhesive.

Optionally, the first outer support member and first intermediate support members may be in coplanar or substantially coplanar alignment. Further, the first outer support member and first intermediate support member may be disposed on opposing sides of the first connecting member. Preferably, the first connecting member interconnects the first outer support member and first intermediate support member. Additionally, the first connecting member may zig zag along the longitudinal axis of the thermally broken truss. Ideally, the first connecting member may be unitarily formed and/or continuous.

Optionally, the second outer support member and second intermediate support member may be in coplanar or substantially coplanar alignment. Further, the second outer support member and second intermediate support member may be disposed on opposing sides of the second connecting member. Preferably, the second connecting member interconnects the second outer support member and second intermediate support member. Additionally, the second connecting member may zig zag along the longitudinal axis of the thermally broken truss. Ideally, the second connecting member may be unitarily formed and/or continuous.

Advantageously, the first and second connecting members act as a brace between the first intermediate support member and the first outer support member and, the second intermediate support member and the second outer support member, respectively, and maintain these at a fixed distance apart. Beneficially, the first and second connecting members reduce the risk of the first and second intermediate support members and the first and second outer support members bending or deforming under an applied load. Additionally, when a truss is cut to size, there is a tendency for struts of a non-continuous connecting member to spring out of position as they are under a certain amount of internal tension during cutting. This risk is minimised by having a unitarily formed and/or continuous connecting member.

Preferably, the first connecting member may form a plurality of triangles with the first outer support member and first intermediate support member. In addition, the second connecting member may form a plurality of triangles with the second outer support member and second intermediate support member. Optionally, the plurality of triangles may be equilateral or isosceles triangles.

Preferably, the first connecting member may be welded to the first outer support member and first intermediate support member. In addition, the second connecting member may be welded to the second outer support member and second intermediate support member.

Optionally, a lateral cross-section of any or more of the first and second outer support members or first and second intermediate support members may be circular, or substantially circular. Further, the diameter of any two or more of the first and second outer support members or first and second intermediate support members may be different. Alternatively, the diameter of any two or more of the first and second outer support members or first and second intermediate support members may be the same. In one embodiment, any or more of the first and second outer support members or first and second intermediate support members may be substantially flat elongate plates.

Advantageously, this means that a variety of different first and second intermediate support members or first and second outer support members may be used, depending on the user requirements of a particular thermally broken truss. If any of the first and second outer support members or first and second intermediate support members are substantially flat elongate plates, these may overlap and provide a large surface area for any thermally insulative fastener to be adhered to.

Preferably, the first and second outer support members and the first and second intermediate support members may be in coplanar alignment. Alternatively, the first outer support member and the first intermediate support member may be offset from the second outer support member and the second intermediate support member.

Preferably, the first and second outer support members may further be sheathed in an insulative material of substantially the same form as the thermally insulative fastener.

This is helpful in adding another layer of thermal insulation, further reducing or preventing thermal energy transfer from the first and second outer support members to the first and second connecting members and across the thermally broken truss.

According to a second aspect of the present invention, there is provided a thermally broken structural building panel comprising: at least one insulation member; at least two thermally broken trusses in accordance with the first aspect of the invention; and at least one strapping member, wherein the thermally broken trusses are arranged in substantially parallel planes and the insulation member is disposed intermediate the thermally broken trusses, the strapping member interconnecting the at least two thermally broken trusses and extending substantially perpendicularly to the at least two thermally broken trusses for retaining the insulation member therebetween.

This construction is beneficial due to the presence of the earlier described thermally broken trusses as part of the structural building panel.

The insulation member improves the thermal insulation properties of the structural building panel, thereby contributing to a strong, lightweight and insulated prefabricated panel.

Preferably, a plurality of insulation members, thermally broken trusses and strapping members are provided. More preferably, at least two of the said insulation members are joined together using joining means. Furthermore, the insulation member may be composed of or include polystyrene, polyurethane, or polyamide. Beneficially, these materials provide good thermal insulation.

This thermally broken structural building panel is beneficial not only for the environment, but also for the building owner/occupier, whose heating bills will be correspondingly lower in the long term. Notably, a thermally broken structural building panel incorporating the thermally broken truss, improves the standard insulation rate of a building.

According to a third aspect of the present invention, there is provided a thermally broken truss for a cage of a structural building panel, comprising: at least two modular units, each modular unit including, elongate first and second support members defining longitudinal edge portions of the modular unit, the first and second support members being adjacent to and in spaced parallel or substantially parallel relationship with one another; and at least one connecting member which extends between the longitudinal edge portions and which interconnects the first and second members, each modular unit being coplanar or substantially coplanar and arranged in a spaced parallel or substantially parallel relationship with one another, the spaced relationship between the modular units defining a gap; a thermally insulative fastener disposed in the gap intermediate a pair of parallel modular units interconnecting the at least two modular units; and a reinforcement element reinforcing the interconnection between the or each pair of parallel modular units and the thermally insulative fastener interconnecting the at least two modular units, whereby the gap and the thermally insulative fastener together substantially provide a thermal break between coplanar modular units.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view from above of a thermally broken truss, in accordance with the invention.

FIG. 2 shows a cross sectional view of the thermally broken truss taken along line A-A in FIG. 1.

FIG. 3 shows a plan view from above of the thermally broken truss shown in FIG. 1.

FIG. 4 shows a perspective view from above of a plurality of the thermally broken trusses, shown in FIG. 1.

FIG. 5 shows a perspective view of a thermally broken structural building panel in accordance with the second aspect of the invention, which incorporates the thermally broken truss of FIG. 1.

FIG. 6 shows perspective view from the side of a thermally broken structural building panel in accordance with the second aspect of the invention, which incorporates the thermally broken truss of FIG. 1.

Referring to the drawings, a thermally broken truss for a cage of a structural building panel is indicated generally at 10. The thermally broken truss comprises first and second longitudinal outer support members 12, 14; first and second elongate intermediate support members 16, 18 interposed between the first and second outer support members 12, 14; at least one first connecting member 20 interconnecting the first outer support member 12 and the first intermediate support member 16; at least one second connecting member 22 interconnecting the second outer support member 14 and the second intermediate support member 18; and a thermally insulative fastener 24 which fastens the first and second intermediate support members 16, 18 together in spaced apart relationship, thereby providing a thermal break between the first and second outer support members 12, 14.

The first and second outer support members 12, 14 and first and second intermediate support members 16, 18 are preferably rigid or substantially rigid struts of wire or cord, and may be or include metal, for example, steel. Typically, the first and second outer support members 12, 14 and first and second intermediate support members 16, 18 are made from a drawing process. It is envisaged that suitable alternative materials and manufacturing processes may be used, if available. The first and second outer support members 12, 14 and first and second intermediate support members 16, 18 are the main load bearing structural elements of the thermally broken truss 10 through which most of any applied load is transmitted. The length of the first and second outer support members 12, 14 and first and second intermediate support members 16, 18 may be in a range of 100 to 6000 mm.

The first and second outer support members 12, 14 and first and second intermediate support members 16, 18 may have a circular lateral cross section. In such an arrangement, the diameter of any two or more of the first and second outer support members 12, 14 or first and second intermediate support members 16, 18 may be the same or different. Preferably the diameter of the first and/or second outer support members 12, 14 and the first and/or second intermediate support members 16, 18 is in a range of 1 to 6 mm. More preferably, the diameter of the first and/or second outer support members 12, 14 and the first and/or second intermediate support members 16, 18 is in a range of 2 to 8 mm. Although preferably circular, the lateral cross-section may be non-circular, such as polygonal, for example, square or rectangular.

Alternatively, any or more of the first and second outer support members 12, 14, and first and second intermediate support members 16, 18 may be substantially flat elongate plates with a rectangular lateral cross section. Preferably, the rectangular lateral cross section of the first and/or second outer support members 12, 14 and the first and/or second intermediate support members 16, 18 is in a range of 30 to 70 mm by 260 to 340 mm. More preferably the rectangular lateral cross section of the first and/or second outer support members 12, 14 and the first and/or second intermediate support members 16, 18 is 50 mm by 300 mm.

The first and second intermediate support members 16, 18 are positioned spaced apart from each other. Preferably, a gap between the first and second intermediate support members 16, 18, defined by the spaced apart relationship, is in the range of 60 to 100 mm, and more preferably, is approximately 60 mm.

A thermally insulative fastener 24 maintains the gap between the first and second intermediate support members 16, 18 relative to one another. In this embodiment, the thermally insulative fastener 24 is preferably a sheath in which the first and second support members are held. The thermally insulative fastener 24 advantageously encloses both the first and second intermediate support members and may have a substantially circular lateral cross section. Preferably, the thermally insulative fastener covers the length of the first and second intermediate support members 16, 18. Consequently, there is provided a thermal break between the first and second intermediate support members 16, 18, and thermal energy flow from the first intermediate support member 16 to the second intermediate support member 18, or vice versa, is greatly reduced.

Although the thermally insulative fastener 24 is continuous, it may be discontinuous forming a plurality of thermally insulative fasteners disposed between the first and second intermediate support members 16, 18. It should be noted that air is known to be a reasonable thermal insulator and so, provided the thermally insulative fastener(s) act to maintain the spaced relationship between the first and second intermediate support members 16, 18, the thermally insulative fastener(s) need not extend the full length of the first and second intermediate support members 16, 18. It will also be appreciated that other configurations of a thermally insulative fastener may be utilised instead. The thermally insulative fastener may instead be provided solely in the gap between the first and second intermediate support members 16, 18 and may be adhered to at least one of the first and second intermediate support members 16, 18 using joining means. The joining means may be or include adhesive.

Typically, the thermally insulative fastener 24 is or includes polystyrene and preferably expanded polystyrene. Polyurethane may be used instead, or indeed any fastener providing some thermal break between the first and second intermediate support members, such a polyamide. Further, the thermally insulative fastener, may be composed of or include adhesive. Advantageously, thermal breaks made of polyamide or polyurethane can be more than a thousand times less conductive than aluminium and a hundred times less than steel.

At least one reinforcement element 26 assists in maintaining the integrity of the thermally insulative fastener, together with the first and second intermediate support members 16, 18. In the drawings, a plurality of reinforcement elements 26 are provided which extend across the first and second intermediate support members 16, 18 and are held in a spaced relationship from the first and second intermediate support members 16, 18 by the thermally insulative fastener 24.

The or each reinforcement element 26 extends across and is connected to the thermally insulative fastener 24. Preferably, the or each reinforcement element 26 may take the form of a strap or collar and encircle the thermally insulative fastener 24; and consequently, also encircle the first and second intermediate support members 16, 18.

Advantageously, to aid the reinforcement mechanism of the reinforcement element 26, the or each reinforcement element 26 may be or may include metal. Consequently, in order to maintain the thermal efficiency of the thermally broken truss 10, the or each reinforcement element 26 is spaced apart from the first and second intermediate connecting members 16, 18.

The first outer support member 12 and first intermediate support member 16 are in coplanar or substantially coplanar alignment. The distance between the first outer support member 12 and first intermediate support member 16 is preferably in a range of 30 mm to 90 mm. More preferably, the distance is in a range of 40 mm to 80 mm. The second outer support member 14 and second intermediate support member 18 are in coplanar or substantially coplanar alignment. The distance between the second outer support member 14 and second intermediate support member 18 is preferably in a range of 30 mm to 90 mm. More preferably, the distance is in a range of 40 mm to 80 mm.

The first connecting member 20 interconnects the first outer support member 12 and first intermediate support member 16. Preferably, the first connecting member 20 is a preferably rigid and continuous wire or cord-like strut similar to the first and second outer support members 12, 14 and/or the first and second intermediate support members 16, 18 and may be or include metal. The first connecting member 20 may have a circular or non-circular lateral cross-section. Preferably, the diameter of the first connecting member 20 is in a range of 1 mm to 8 mm. The cross sectional area of the first connecting member 20 may be the same of different to that of the first and second outer support members 12, 14 and/or the first and second intermediate support members 16, 18.

Beneficially, the first connecting member 20 braces the first outer support member 12 and first intermediate support member 16 at a fixed distance apart. Advantageously, this reduces the risk of the first outer support member 12 and first intermediate support member 16 bending or deforming under an applied load.

Instead of being continuous, the first connecting member 20 may be discontinuous and alternatively, may comprise a plurality of discrete struts. Such struts made be made from length lengths of rigid wire or cord, typically 30 to 120 mm long. When a thermally broken truss 10 is cut to size, there is a tendency for the struts of a non-continuous connecting member to spring out of position since they are under a certain amount of internal tension during cutting. However, the risk is minimised by using a unitarily formed and/or continuous connecting member.

The first connecting member 20 preferably zig zags along the longitudinal extent of the first outer support member 12 and first intermediate support member 16. The first connecting member 20 may form a series of triangles 28 with the first outer support member 12 and first intermediate support member 16. Preferably, the triangles 28 are equilateral triangles, but they may be isosceles or right-angled triangles instead.

Alternatively, if the first connecting member 20 is a non-connecting member as described above, the individual struts may each pass diagonally from first outer support member 12 to the first intermediate support member 16, or vice versa.

The first connecting member 20 is connected to the first outer support member 12 and first intermediate support member 16 at or adjacent to each bend or apex 30 of a plurality of nodes 32. Advantageously, the nodes 32 help to rigidify the thermally broken truss 10 and protect the integrity of the thermally broken truss 10 from deformation under a non-uniform load. Each node 32 is preferably achieved through a spot weld. However, alternative types of fixing means may be used provided that a permanent connection is made.

In compression, deformation of the first connecting member 20 is most likely to occur at or in close proximity to each bend or apex 30 of each zig zag. By placing the nodes 32 at or very proximate each bend or apex 30, the thermally broken truss's resistance to buckling is increased. Such positioning of the nodes 32 significantly increases the load bearing capability of the thermally broken truss 10.

By having discreet nodes 32, the rigidity of the thermally broken truss 10 is improved, thereby making the thermally broken truss 10 more resistant to deformation especially under non-uniform loads, for example, during high winds or earthquakes.

Optionally, there may be a further first connecting member disposed between the first outer support member 12 and first intermediate support member 16. The further first connecting member is substantially the same as the first connecting member 20, and therefore further detailed description is omitted. Similarly to the first connecting member 20, the further first connecting member may be connected to the first outer support member 12 and first intermediate support member 16, at an additional plurality of nodes. The additional nodes may be similar to the nodes previously described, but spaced from the first said nodes 32. The benefit of a further first connecting member is that its presences increases the nodal connections and therefore further improves the rigidity of the thermally broken truss 10. Similarly to the first connecting member 20, the further first connecting member may be a non-continuous connecting member. In such an arrangement, the struts may preferably extend between the first outer support member 12 and first intermediate support member 16 in an opposite direction to that of the first connecting member 20, with the combination of first connecting member 20 and further first connecting members forming a lattice arrangement.

The second connecting member 22 interconnects the second outer support member 14 and second intermediate support member 18. The second connecting member 22 is substantially the same as the first connecting member 20, and therefore further detailed description is omitted.

The first and second outer support members 12, 14 and the first and second intermediate support members 16, 18 are preferably arranged in coplanar, or substantially coplanar, alignment, as best illustrated in FIG. 3, with the first and second connecting members 20, 22 offset from one another.

It will be appreciated that, while a specific configuration of the first and second outer support members 12, 14 and the first and second intermediate support members 16, 18 and the first and second connecting members 20, 22 is shown and described herein, this is not limited to any particular design, configuration or embodiment. For example, the first outer support member 12 and the first intermediate support member 16 may be offset from the second outer support member 14 and the second intermediate support member 18, with the first and second connecting members 20, 22 in coplanar alignment.

At least one bracing element 34 may be used to help brace the first and second outer support members 12, 14 of the thermally broken truss 10 and maintain them at a fixed distance apart. In this embodiment, the bracing element 34 is provided as a horizontal or substantially horizontal tie, which extends across and interconnects first and second outer support members 12, 14 and first and second intermediate support members 16, 18. Each bracing element 34 extends across and is connected to the thermally broken truss at at least the first and second outer support members 12, 14. However, each bracing element 34 may be connected to each of the first and/or second outer support members 12, 14 and/or each of the first and/or second intermediate members 16, 18. Connection is preferably achieved by welding.

Preferably, each bracing element 34 may be housed in a further insulative material 36 of the or substantially the same form as the thermally insulative fastener 24. Beneficially, this prevents thermal energy transfer in a vertical direction.

Further, each of the first and/or second outer support members 12, 14 may be sheathed in an insulative material 38 of the or substantially the same form as the thermally insulative fastener 24.

In FIGS. 5 and 6, a thermally broken structural building panel is indicated generally at 40. The structural building panel comprises a plurality of insulation members 42 and plurality of the thermally broken trusses 10. Features in common with the first aspect of the invention are denoted by the same reference numerals, for example component parts of the thermally broken truss 10 are indicated.

In this embodiment, each thermally broken truss 10 has first and second outer support members 12, 14, first and second intermediate support members 16, 18, first and second connecting members 20, 22, a thermally insulative fastener 24, a plurality of reinforcement elements 26, and a bracing element 34. Preferably, each of the bracing element 34 and first and second outer support members 12, 14 and are sheathed in insulative material 36, 38 of the or substantially the same form as the thermally insulative fastener 24.

One insulation member 42 is disposed between each pair of thermally broken trusses 10. Preferably, the material of the insulation member 42 provides good thermal insulation. The insulation member 42 may be or may include a low density material, for example polystyrene, or more preferably expanded polystyrene. Polyurethane foam may be used instead. Polyurethane foam is a better insulator than polystyrene but it is less environmentally friendly than polystyrene.

Optionally, the insulation member 42 takes the form of a rectangular block. Exemplary dimensions of the insulation member 42 are: 2400 mm (length)×40 mm (width)×50 mm (depth). Selection of the depth is important to the extent that it permits the insulation member 42 to be fitted between adjacent thermally broken trusses 10, i.e. the depth of the insulation member 42 must be the same or less than the spacing between adjacent thermally broken trusses 10.

In FIGS. 4 to 6, each thermally broken truss 10 is arranged adjacent to another thermally broken truss 10 in parallel or substantially parallel spaced apart planes. A plurality of vertically spaced elongate retaining or strapping members 44 extend perpendicularly to the thermally broken trusses 10 to interconnect the thermally broken trusses 10 typically via the first and second outer support members 12, 14. The plurality of thermally broken trusses 10 and plurality of strapping members 44 together form a wire framework or cage in which the plurality of insulation members 42 are housed. The strapping members 44 help to keep the insulation members 42 in position between adjacent thermally broken trusses 10.

It is advantageous if there is a clearance between the insulation members 42 and the cage once assembled together, as described in more detail below.

The strapping members 44 also maintain the thermally broken trusses 10 at a fixed or substantially fixed distance apart. A typical spacing between adjacent thermally broken trusses 10 is in a range of 40 mm to 60 mm, and more preferably the spacing is approximately 50 mm. The strapping members 44 are positioned at regular intervals along the longitudinal extent of the thermally broken truss 10, typically every 50 mm.

Each strapping member 44 is a preferably rigid wire or cord-like strut, and may be or include metal. Each strapping member 44 may have a circular or non-circular lateral cross-section. The diameter of each strapping member 44 may be in a range of 1 mm to 6 mm. However, the strapping members 44 may be planar and provided as, for example, a continuous sheet or alternatively a mesh, which extends along or around at least a portion of the thermally broken structural building panel 40.

The strapping members 44 are preferably mounted to the thermally broken trusses at a plurality of positions using fixing means 46. Each strapping member 44 may be connected to every other thermally broken truss 10. However, alternative interval spacing may be considered, for example, a connection between each strapping member 44 and every thermally broken truss 10, or, a connection between each strapping member 44 and every third thermally broken truss 10. Preferably, the fixing means 46 is a spot weld. Alternatively, the fixing means 46 may include a loop provided on one or more of the first and/or second outer support members 12, 14, through which the strapping member 44 passes, thereby securing the strapping member 44 to the thermally broken truss 10.

To form the thermally broken structural building panel 40, the thermally broken trusses 10 and insulation members 42 are assembled together in an alternating sequence. If desired, the insulation members 42 are connected together during assembly using joining means. Such joining means may be or include an adhesive. The strapping members 44 are then connected to the thermally broken trusses 10.

With the thermally broken structural building panel 40 on site, a concrete and/or plaster render 48 is applied to opposing faces of the thermally broken structural building panel 40. Advantageously, the render 48 may add additional strength to the wire cage, if so required. The render 48 bonds to the first and second outer support members 12, 14, and to the strapping members 44. As it is intended that there is a clearance between at least an outwardly facing portion of the insulation member 42 and the wire cage, beneficially, the render 48 is able to enter the confines of the cage and bond to and around the first and second outer support members 12, 14 and the strapping members 44 from within the cage as well as outside of the cage. The bonding helps to improve the overall load bearing capacity of the thermally broken structural building panel 40, as the surface area available for bonding is increased.

The render 48 typically comprises a weatherproofing mix of Portland cement, aggregates and sand. Alternatives, such as gypsum plaster, are commonly used for rendering internal surfaces. The layer of cement or plaster 48 encases the mesh cage on both sides of the core producing a strong and rigid structure when dry. If desired, various waterproofing, anti- fungal and fibre reinforcing agents may be applied to the rendering mixture or the dried surface. Internal and external surfaces are defined in this context as such relative to the constructed building. 

1. A thermally broken truss for a cage of a structural building panel, comprising: first and second elongate outer support members; first and second elongate intermediate support members interposed between the first and second outer support members; at least one first connecting member interconnecting the first outer support member and the first intermediate support member; at least one second connecting member interconnecting the second outer support member and the second intermediate support member; and a thermally insulative fastener which fastens the first and second intermediate support members together in spaced apart relationship, thereby providing a thermal break between the first and second elongate outer support members.
 2. A thermally broken truss as claimed in claim 1, wherein the thermally insulative fastener is a sheath in which the first and second intermediate support members are received.
 3. A thermally broken truss as claimed in claim 1, further comprising at least one reinforcement element which buttresses the thermally insulative fastener and is held in a spaced apart relationship from the first and second intermediate support members by the thermally insulative fastener.
 4. A thermally broken truss as claimed in claim 3, wherein the reinforcement element is: a strap; a collar; or is or includes metal.
 5. (canceled)
 6. (canceled)
 7. A thermally broken truss as claimed in claim 3, wherein the reinforcement element encircles at least part of the thermally insulative fastener.
 8. (canceled)
 9. (canceled)
 10. A thermally broken truss as claimed in claim 1, wherein the thermally insulative fastener is provided in a gap between the first and second intermediate support members, and wherein the thermally insulative fastener is connected to at least one of the first or second intermediate support members using adhesive.
 11. (canceled)
 12. (canceled)
 13. (canceled)
 14. A thermally broken truss as claimed in claim 1, wherein the first outer support member and first intermediate support members are in coplanar or substantially coplanar alignment, and/or the second outer support member and second intermediate support members are in coplanar or substantially coplanar alignment.
 15. A thermally broken truss as claimed in claim 1, wherein the first connecting member zig zags along the longitudinal axis of the thermally broken truss, and/or the second connecting member zig zags along the longitudinal axis of the thermally broken truss.
 16. A thermally broken truss as claimed in claim 1, wherein the first connecting member is unitarily formed and/or wherein the second connecting member is unitarily formed.
 17. (canceled)
 18. (canceled)
 19. (canceled)
 20. A thermally broken truss as claimed in claim 1, wherein the first connecting member forms a plurality of triangles with the first outer support member and first intermediate support member, and/or the second connecting member forms a plurality of triangles with the second outer support member and second intermediate support member.
 21. (canceled)
 22. (canceled)
 23. A thermally broken truss as claimed in claim 1, wherein the first connecting member is welded to the first outer support member and first intermediate support member, and/or the second connecting member is welded to the second outer support member and second intermediate support member.
 24. (canceled)
 25. A thermally broken truss as claimed in claim 1, wherein a lateral cross-section of one or more of the first and second outer support members and/or first and second intermediate support members is or is substantially circular.
 26. A thermally broken truss as claimed in claim 1, wherein a dimension of any two or more of the first and second outer support members and/or first and second intermediate support members is different.
 27. (canceled)
 28. A thermally broken truss as claimed in claim 1, wherein one or more of the first and second outer support members and/or first and second intermediate support members are or are substantially flat plates.
 29. (canceled)
 30. A thermally broken truss as claimed in claim 1, wherein the first outer support member and the first intermediate support member are offset from the second outer support member and the second intermediate support member.
 31. A thermally broken truss as claimed in claim 1, wherein at least part of any or more of the first and second outer support members are sheathed in an insulative material of the or substantially the same form as the thermally insulative fastener.
 32. A thermally broken structural building panel comprising: at least one insulation member; at least two thermally broken trusses as claimed in claim 1; and at least one strapping member, wherein the thermally broken trusses are arranged in substantially parallel planes and the insulation member is disposed intermediate the thermally broken trusses, the strapping member interconnecting the at least two thermally broken trusses and extending substantially perpendicularly to the at least two thermally broken trusses for retaining the insulation member therebetween.
 33. A thermally broken structural building panel as claimed in claim 32, wherein a plurality of insulation members, thermally broken trusses and strapping members are provided, wherein at least two of the said insulation members are joined together using adhesive.
 34. (canceled)
 35. (canceled)
 36. A thermally broken structural building panel as claimed in claim 33, wherein the insulation member is or includes any one of polystyrene, polyurethane or polyamide.
 37. (canceled)
 38. A thermally broken truss for a cage of a structural building panel, comprising: at least two modular units, each modular unit including: elongate first and second support members defining longitudinal edge portions of the modular unit, the first and second support members being adjacent to and in spaced parallel or substantially parallel relationship with one another; and at least one connecting member which extends between the longitudinal edge portions and which interconnects the first and second members, each modular unit being coplanar or substantially coplanar and arranged in a spaced parallel or substantially parallel relationship with one another, the spaced relationship between the modular units defining a gap; a thermally insulative fastener disposed in at least part of the gap intermediate a pair of parallel modular units interconnecting the at least two modular units; and a reinforcement element reinforcing the interconnection between the or each pair of parallel modular units and the thermally insulative fastener interconnecting the at least two modular units, whereby the gap and the thermally insulative fastener together substantially provide a thermal break between coplanar modular units. 